This application relates to the art of chucks and, more particularly, to chucks of the type used for holding workpieces to be operated on by boring or milling equipment. Although the invention is particularly applicable to chucks of the type used for holding workpieces stationary on a table while operating on the workpiece with boring or milling equipment, it will be appreciated that the invention has broader aspects and may be used for other purposes and in other environments including lathes and the like.
It is very common to have chucks which operate by either externally or internally gripping a workpiece while simultaneously pulling same down against stops for rigidly holding the workpiece stationary while performing machining operations thereon. In many prior arrangements, completely separate chucks are required for performing external and internal gripping action, and the need for two completely independent chuck assemblies is very expensive. In addition, complete removal of one chuck assembly from an associated machine or apparatus is time consuming.
Certain prior chuck assemblies have included arrangements for converting the chuck mechanism between two different configurations for either externally gripping a workpiece while simultaneously pulling same down against stops or internally gripping a workpiece while simultaneously pulling same downwardly against stops. Previous arrangements of this type have, however, been relatively complicated to convert or have not provided optimum gripping and pulling action in both configurations while affording high accuracy and repeatability.
It has, therefore, been considered desirable to provide a chuck assembly with features enabling selective convertibility between two different configurations for gripping a workpiece either externally or internally, while simultaneously pulling the workpiece down against stops in either configuration. The subject invention meets these needs and others while overcoming problems previously encountered with prior art chucking devices.